forum.funcube.org.uk

The main aim of the FUNcube project is provide educationalists access to information about a real spacecraft in Low Earth Orbit. Please use this forum to discuss classroom projects and similar matters. FUNcube support is provided elsewhere in the forum.

After approaching 2 months in orbit, we have enough FC data to do some longitudinal looks. I noticed the other day that the max temperatures of the MSE panel bars had gone up about 5 degrees, that prompted me to look at the rotation rate, and I noticed a dramatic decrease in the rotation rate. From about day one, the satellite went from a rotation rate of 2.5 minutes per revolution down to about 1.45 minutes per revolution on December 28th...about 37 days on orbit, but then after that the satellite rotation rate has really taken a nose dive and today the rotation rate is at about 5.5 minutes per revolution. If you would like to see the graphic of my data, contact me a mspencer@arrl.org. Are others seeing the same thing?

Did something happened around December 28th to cause the rotation rate to decrease? I have no idea why, I don’t see any reported solar activity around that date that could cause this to happen. It will be interesting to see what happens in the future. The rotation rate is getting to the point that it is hard to determine using the high resolution data and I have had to switch over to the WOD to pull the numbers.

It is very, very curious to me.

Any ideas?

This particular situation is why the FUNCube telemetry can be such a powerful educational tool. I would like to hear more about schools that are analyzing the FC data in their classroom students.

Is it possible to download or acquire historic data? Example I want to fill in gaps of what I have collected, or in this case, I want to review data for a period where I haven't collected data. say for the period of Dec 25, 2013 through Jan 1, 2014? If it is possible, how does one go about getting pat data?

FUNcube-1 incorporates a Passive Attitude Control System. This comprises of a single magnet and two hysteresis rods. This configuration is pretty standard system. It is intended that the spacecraft will rotate around its Z axis so that no individual panel is facing the sun for extended periods of time.

We have a large amount of telemetry that shows the spacecraft attitude and we have noticed that the rotation period has been varying quite dramatically since launch.

Colin, VK5HI, has kindly produced this graph which shows the detail- we are still uncertain about the reasons for these changes occurring - all ideas and suggestions about what will happen next will be received with interest!

The FUNCube is a bird that just keeps on giving. Today, my data indicates that the FC has passed a rotation rate mile stone and it has dipped above 1 RPM, from the previous low of around 8.5 minutes-per-revolution (.12 RPM). I am still unclear as to what may have happened on December 28th that caused the rotation rate turn around, nor am I any more clear as to the mechanism that caused the rate to slow down to the minimum and now spool up to the current rate. All indicators point to continued rotation rate increase (at probably a natural log track). It is also interesting that there appears to be a correlation between the MSE panel maximum temperatures and the rotation rate. Even though the thermal exposure of the MSE panels is at 25% throughout (when the panels are facing the sun they are illuminated 25% of the rotation), the heating of the panels tracks the rotation rate. I have come to the conclusion that the dynamic nature of the heating of the MSE panels has a significant impact on the behavior being observed during the MSE...of course I can't explain that either. [There is a definite correlation between the magnitude of the temperature excursions from a smooth curve to the rotation rate, that helps to quantify the differences in the emissivity/absorptivity of the two MSE panels.]

One other observation while I am at it is the change in the Z-axis wobble as a function of the rotation rate. By observing the deviations of the high res +Z-axis panel plot over time, the excursions from a smooth plot when the rotation rate was at the minimum were far greater than the excursions at the higher rotation rate. What I glean from this observation is that the higher rotation rate has the benefit of stabilizing any Z-axis wobble that may result from the flip Z-axis flip maneuvers during the orbit. Purely conjecture on my part.

In my view, the FC continues to out perform the expected education outcomes. There is a huge benefit from the questions generated...more so than the answers. This thing, in the hands of the right teachers, targets STEM education spot on.

Thanks for that link, extremely helpful. I have done some preliminary study on the concept and think the follow-on, the YORP Effect, is more appropriate. Could it be that by accident or by design that the configuration of the FUNCube and/or the way the MSE is installed is allowing us to see the YORP Effect? The most recent article I have been able to find on YORP Effect is from 2007 and focused on small asteroids. Perhaps FC allows us to see the YORP Effect without waiting a thousand years for a passing asteroid to revisit Earth.

HelloI want to write a piece on this topic in our magazine. May I use this picture of this graph in the article?

best regards

Henk

wa8sme wrote:The FUNCube is a bird that just keeps on giving. Today, my data indicates that the FC has passed a rotation rate mile stone and it has dipped above 1 RPM, from the previous low of around 8.5 minutes-per-revolution (.12 RPM). I am still unclear as to what may have happened on December 28th that caused the rotation rate turn around, nor am I any more clear as to the mechanism that caused the rate to slow down to the minimum and now spool up to the current rate. All indicators point to continued rotation rate increase (at probably a natural log track). It is also interesting that there appears to be a correlation between the MSE panel maximum temperatures and the rotation rate. Even though the thermal exposure of the MSE panels is at 25% throughout (when the panels are facing the sun they are illuminated 25% of the rotation), the heating of the panels tracks the rotation rate. I have come to the conclusion that the dynamic nature of the heating of the MSE panels has a significant impact on the behavior being observed during the MSE...of course I can't explain that either. [There is a definite correlation between the magnitude of the temperature excursions from a smooth curve to the rotation rate, that helps to quantify the differences in the emissivity/absorptivity of the two MSE panels.]

One other observation while I am at it is the change in the Z-axis wobble as a function of the rotation rate. By observing the deviations of the high res +Z-axis panel plot over time, the excursions from a smooth plot when the rotation rate was at the minimum were far greater than the excursions at the higher rotation rate. What I glean from this observation is that the higher rotation rate has the benefit of stabilizing any Z-axis wobble that may result from the flip Z-axis flip maneuvers during the orbit. Purely conjecture on my part.

In my view, the FC continues to out perform the expected education outcomes. There is a huge benefit from the questions generated...more so than the answers. This thing, in the hands of the right teachers, targets STEM education spot on.

Sure, please feel free to use the graphics that I presented (I can't speak however for graphics posted by others). I have uploaded the most current graphics. The rotation rate of the bird has started to slow down again, just another learning opportunity presented by this resource.